I just found this creature in a pot in my backyard. For perspective, it's about 8 inches high and the bell shaped top is almost the size of my fist. Someone here says it's a "Shaggy Mane". I've never seen anything like it before.
That's the oddest fungi I have ever seen. It may actually be an ever-evolving new variety. I'm sure your local college has a resident mycologist. Call him/her and see if they can ID it. Regardless, I'd cut it down and bag it just in care it's rare.
That said, you might want to bite a piece off and see what effect it has on you. What's a little kidney or liver failure in the pursuit of science, right?